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54 DESIGN007 MAGAZINE I AUGUST 2024 Asymmetric Hybrid Printed Circuit Board Design: Warpage Considerations Article by Kaspar Tsang, Gause Hu, Jimmy Hsu, Aje Chang, Alan Sun, Brian Ho, Ryan Chang, and Thonas Su Editor's note: is excerpt is om a white paper presented at IPC APEX EXPO 2024, and is intended to give an overview and recommen- dation on the topic. To see a list of full papers and other conference proceedings, please click here. Abstract e printed circuit board (PCB) accounts for a significant portion of the PCBA's (printed circuit board assembly) BOM (bill of material) cost. Designs with hybrid PCB stackup are adopted to reduce the cost of the PCB by using less expensive laminate materials in layers that do not have routings for high-speed signals (e.g., power and ground layers). e conven- tional hybrid PCB stackup design is symmetri- cal in the middle 1 . is engineering technique has been employed in the data center industry for quite some time. To extend the idea and optimize the purpose of hybrid PCB stackup design, the feasibility of an asymmetric hybrid stackup is currently being studied. Asymmetric hybrid stackup offers greater flexibility and potential cost savings in high-speed traces routing 2 . However, the mechanical reliability risks in the asymmet- ric hybrid stackup are even more challeng- ing than those in conventional hybrid PCB stackup. In this research, a team with diverse expertise, including design, material, and PCB manufacture process, was formed to study the effects of (1) different hybrid mate-